Pounds per square inch
Pounds per square inch or PSI is an imperial unit of pressure. Using the imperial units of pounds and square inches, it is a measure of force per unit area. Therefore, 1 PSI is measured as one pound of force applied per one square inch. Since it is acting on a much smaller area than the pascal, 1 PSI is much more pressure than 1 pascal (metric unit). PSI is a non-[SI] unit, British unit that is now obsolete.
- Psia: when pressure is measured with respect to vacuum. This is known as absolute pressure.
- Psig: when pressure is measured with respect to atmospheric pressure. This is known as gauge pressure.
- Psid: when the difference of pressure is measured between two points in the environment. This is known as differential pressure.
For Further Reading
- A. Atkins and M. Escudier, A dictionary of mechanical engineering. Oxford: Oxford University Press, 2013.
- C. Schaschke, Dictionary of Chemical Engineering, A. Oxford University Press, USA, 2014.